Apparatus and system for swing adsorption processes

ABSTRACT

Provided are apparatus and systems for performing a swing adsorption process. This swing adsorption process may involve performing a startup mode process prior to beginning a normal operation mode process to remove contaminants from a gaseous feed stream. The startup mode process may be utilized for swing adsorption processes, such as TSA and/or PSA, which are utilized to remove one or more contaminants from a gaseous feed stream.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication 62/343,426, filed May 31, 2016, entitled APPARATUS ANDSYSTEM FOR SWING ADSORPTION PROCESSES, the entirety of which isincorporated by reference herein.

FIELD

The present techniques relate to a method and system associated withswing adsorption processes used in conditioning streams for downstreamprocessing. In particular, the method and system involve a startup modeprocess for a swing adsorption process, which is further utilized forstarting downstream process.

BACKGROUND

Gas separation is useful in many industries and can typically beaccomplished by flowing a mixture of gases over an adsorbent materialthat preferentially adsorbs one or more gas components while notadsorbing one or more other gas components. The non-adsorbed componentsare recovered as a separate product.

One particular type of gas separation technology is swing adsorption,such as temperature swing adsorption (TSA), pressure swing adsorption(PSA), partial pressure swing adsorption (PPSA), rapid cycle temperatureswing adsorption (RCTSA), rapid cycle pressure swing adsorption (RCPSA),rapid cycle partial pressure swing adsorption (RCPPSA), and not limitedto but also combinations of the fore mentioned processes, such aspressure and temperature swing adsorption. As an example, PSA processesrely on the phenomenon of gases being more readily adsorbed within thepore structure or free volume of an adsorbent material when the gas isunder pressure. That is, the higher the gas pressure, the greater theamount of readily-adsorbed gas adsorbed. When the pressure is reduced,the adsorbed component is released, or desorbed from the adsorbentmaterial.

The swing adsorption processes (e.g., PSA and/or TSA) may be used toseparate gases of a gas mixture because different gases tend to fill themicropore of the adsorbent material to different extents. For example,if a gas mixture, such as natural gas, is passed under pressure througha vessel containing an adsorbent material that is more selective towardscarbon dioxide than it is for methane, at least a portion of the carbondioxide is selectively adsorbed by the adsorbent material, and the gasexiting the vessel is enriched in methane. When the adsorbent materialreaches the end of its capacity to adsorb carbon dioxide, it isregenerated by reducing the pressure, thereby releasing the adsorbedcarbon dioxide. Then, the adsorbent material is typically purged andrepressurized prior to starting another adsorption cycle.

The swing adsorption processes typically involve adsorbent bed units,which include adsorbent beds disposed within a housing and configured tomaintain fluids at various pressures for different steps in a cyclewithin the unit. These adsorbent bed units utilize different packingmaterial in the bed structures. For example, the adsorbent bed unitsutilize checker brick, pebble beds or other available packing. As anenhancement, some adsorbent bed units may utilize engineered packingwithin the bed structure. The engineered packing may include a materialprovided in a specific configuration, such as a honeycomb, ceramic formsor the like.

Further, various adsorbent bed units may be coupled together withconduits and valves to manage the flow of fluids through the cycle.Orchestrating these adsorbent bed units involves coordinating the stepsin the cycle for each of the adsorbent bed units with other adsorbentbed units in the system. A complete cycle can vary from seconds tominutes as it transfers a plurality of gaseous streams through one ormore of the adsorbent bed units.

As may be appreciated, the removal of contaminants may result in theprocess operating in different modes, such as a startup mode and anormal operation mode. The startup mode may be utilized to prepare theequipment (e.g., the adsorbent bed and various stream) for the normaloperation mode. The normal operation mode may be utilized when theprocess is receiving various streams, such as the gaseous feed stream,and removing contaminants from the gaseous feed stream to provide aproduct stream, which may be referred to as steady state. For example,the conventional processes may operate in normal operation mode to treathydrocarbon containing streams containing water (H₂O) or carbon dioxide(CO₂) to prepare the stream for downstream processing, such as naturalgas liquid recovery (NGL) or liquefied natural gas (LNG) processing. Thenormal operation modes may be different for each of the respectivedownstream processes based on the respective specifications that areinvolved for normal operational mode. For example, a typical LNGspecification requires the CO₂ content to be less than 50 parts permillion molar (ppm).

During the startup mode, the cycle may be different than the cycleutilized for normal operation mode. Conventional systems may utilize asingle heating step to regenerate the adsorbent material with hightemperatures to remove any contaminants as the startup mode cycle. Forexample, a startup process involving a mole sieve unit may includeheating the bed to temperatures in excess of 550° F.

Unfortunately, conventional startup mode processes have certainlimitations. For example, the process in startup mode may involve merelyheating the adsorbent material to high temperatures. The heating of theadsorbent material to high temperatures in the conventional approachestypically rely upon dedicated high-temperature startup heaters. Theseheaters are expensive, involve large capital expenditure and highoperational costs. In addition, these heaters increase the weight andfootprint of the facility. Further, the cycle time is typically longerthan necessary to remove contaminants to ensure sufficient time isprovided for downstream equipment to begin operations. In addition, thetemperature that the adsorbent material are exposed to may lessen theoperational life of the adsorbent material and may lessen the efficiencyof the adsorbent material.

Accordingly, there remains a need in the industry for apparatus,methods, and systems that provided enhancements to the start-upprocesses associated with hydrocarbon recovery processes. In particular,a need exists for enhancements to startup mode processes for rapid cycleswing adsorption processes.

SUMMARY OF THE INVENTION

In one or more embodiments, the present techniques comprise a processfor removing contaminants from a gaseous feed stream with a swingadsorption process. The process comprising: a) performing a purge step,wherein the purge step comprises passing an external gas stream throughan adsorbent bed unit to remove one or more contaminants from anadsorbent bed within a housing of the adsorbent bed unit to form a purgeproduct stream; b) performing one or more adsorption steps, wherein eachof the one or more adsorption steps comprise passing a gaseous feedstream through an adsorbent bed unit having an adsorbent bed to separateone or more contaminants from the gaseous feed stream to form a productstream; c) determining whether the product stream is within aspecification for a contaminant; d) if the product stream is within thespecification, passing the product stream to a downstream process; ande) if the product stream is not within the specification, repeating thesteps a) to d) for at least one additional cycle.

In yet another embodiment, a cyclical swing adsorption system isdescribed. The system includes a plurality of manifolds; a plurality ofadsorbent bed units coupled to the plurality of manifolds, and anexternal gas bypass valve in fluid communication with purge manifold andconfigured to provide a flow passage for an external gas stream from anexternal gas storage vessel to the purge manifold in a startup modeposition and configured to block the flow passage of the external gasstream from the external gas storage vessel to the purge manifold in anormal operation mode position. The plurality of manifolds comprise afeed manifold configured to pass a feed stream to the plurality ofadsorbent bed units during an adsorption step, a product manifoldconfigured to pass a product stream from the plurality of adsorbent bedunits during the adsorption step, a purge manifold configured to pass apurge stream to the plurality of adsorbent bed units during aregeneration step, a purge product manifold configured to pass a purgeproduct stream from the plurality of adsorbent bed units during theregeneration step. Each manifold of the plurality of manifolds isassociated with one swing adsorption process step of a plurality ofswing adsorption process steps. Each of the adsorbent bed unitscomprises a housing; an adsorbent material disposed within the housing;a plurality of valves, wherein at least one of the plurality of valvesis associated with one of the plurality of manifolds and is configuredto manage fluid flow along a flow path extending between the respectivemanifold and the adsorbent material.

In certain embodiments, the system or method may include certainvariations. The plurality of valves may comprise one or more poppetvalves; the plurality of manifolds and/or the plurality of adsorbent bedunits may be configured to operate at pressures between 0.1 bar absolute(bara) and 100 bara; the system may include a heating unit disposedupstream of the purge manifold and downstream of the external gasstorage vessel, wherein the heating unit may be configured to heat theexternal gas stream to a temperature in the range between a temperaturein the range between 450° F. and the gaseous feed stream temperature orin the range between a temperature in the range between 450° F. andgreater than 100° F. of the gaseous feed stream temperature; the systemmay include a conditioning unit disposed downstream of the purge productmanifold and upstream of the external gas storage vessel, wherein theconditioning unit may be configured to remove one or more contaminantsfrom the purge product stream; wherein the plurality of manifoldsfurther comprise a blowdown manifold configured to pass a blowdownstream from the plurality of adsorbent bed units during a blowdown step;and the system may include a liquefied natural gas process unit in fluidcommunication with the adsorbent bed unit and configured to receive theproduct stream and separate the product stream into a final productstream and a flash fuel stream, wherein the flash fuel stream may bepassed to the purge manifold. Further, the external gas stream maycomprise a nitrogen stream comprising predominately nitrogen with lessthan 0.1 ppm of water, less than 1 ppm of water or less than 10 ppm ofwater or at least one of nitrogen, methane, helium, hydrogen or anycombination thereof.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other advantages of the present disclosure may becomeapparent upon reviewing the following detailed description and drawingsof non-limiting examples of embodiments.

FIG. 1 is a three-dimensional diagram of the swing adsorption systemwith six adsorbent bed units and interconnecting piping in accordancewith an embodiment of the present techniques.

FIG. 2 is a diagram of a portion of an adsorbent bed unit havingassociated valve assemblies and manifolds in accordance with anembodiment of the present techniques.

FIG. 3 is an exemplary flow chart for performing an external startupmode of a swing adsorption process in accordance with an embodiment ofthe present techniques.

FIG. 4 is an exemplary diagram of a startup mode step in accordance withan embodiment of the present techniques.

FIGS. 5A and 5B are exemplary diagrams associated with another startupmode step in accordance with an embodiment of the present techniques.

FIG. 6 is an exemplary diagram associated with yet another startup modestep in accordance with an embodiment of the present techniques.

FIG. 7 is an exemplary diagram associated with another startup mode stepin accordance with an embodiment of the present techniques.

FIG. 8 is an exemplary diagram associated with still another startupmode step in accordance with an embodiment of the present techniques.

FIG. 9 is an exemplary diagram associated with normal operation mode.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise explained, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which this disclosure pertains. The singular terms“a,” “an,” and “the” include plural referents unless the context clearlyindicates otherwise. Similarly, the word “or” is intended to include“and” unless the context clearly indicates otherwise. The term“includes” means “comprises.” All patents and publications mentionedherein are incorporated by reference in their entirety, unless otherwiseindicated. In case of conflict as to the meaning of a term or phrase,the present specification, including explanations of terms, control.Directional terms, such as “upper,” “lower,” “top,” “bottom,” “front,”“back,” “vertical,” and “horizontal,” are used herein to express andclarify the relationship between various elements. It should beunderstood that such terms do not denote absolute orientation (e.g., a“vertical” component can become horizontal by rotating the device). Thematerials, methods, and examples recited herein are illustrative onlyand not intended to be limiting.

As used herein, “stream” refers to fluid (e.g., solids, liquid and/orgas) being conducted through various equipment. The equipment mayinclude conduits, vessels, manifolds, units or other suitable devices.

As used herein, “conduit” refers to a tubular member forming a channelthrough which something is conveyed. The conduit may include one or moreof a pipe, a manifold, a tube or the like.

The provided processes, apparatus, and systems of the present techniquesmay be used in swing adsorption processes that remove contaminants (CO₂,H₂O, and H₂S) from feed streams, such as hydrocarbon containing streams.As may be appreciated and as noted above, the hydrocarbon containingfeed streams may have different compositions. For example, the gaseousfeed stream may be a hydrocarbon containing stream having greater thanone volume percent hydrocarbons based on the total volume of the feedstream. As another example, the hydrocarbon feed streams may vary widelyin amount of acid gas, such as from several parts per million acid gasto 90 volume percent (vol. %) acid gas. Non-limiting examples of acidgas concentrations from exemplary gas reserves sources includeconcentrations of approximately: (a) 4 ppm H₂S, 2 vol. % CO₂, 100 ppmH₂O (b) 4 ppm H₂S, 0.5 vol. % CO₂, 200 ppm H₂O (c) 1 vol. % H₂S, 2 vol.% CO₂, 150 ppm H₂O, (d) 4 ppm H₂S, 2 vol. % CO₂, 500 ppm H₂O, and (e) 1vol. % H₂S, 5 vol. % CO₂, 500 ppm H₂O. Further, in certain applicationsthe hydrocarbon containing stream may include predominately hydrocarbonswith specific amounts of CO₂ and/or water. For example, the hydrocarboncontaining stream may have greater than 0.00005 volume percent CO₂ basedon the total volume of the gaseous feed stream and less than 2 volumepercent CO₂ based on the total volume of the gaseous feed stream; orless than 10 volume percent CO₂ based on the total volume of the gaseousfeed stream. The processing of feed streams may be more problematic whencertain specifications have to be satisfied.

The removal of contaminants may be performed by swing adsorptionprocesses during normal operations to prepare the stream for furtherdownstream processing, such as NGL processing and/or LNG processing. Forexample, natural gas feed streams for liquefied natural gas (LNG)applications have stringent specifications on the CO₂ content to ensureagainst formation of solid CO₂ at cryogenic temperatures. The LNGspecifications may involve the CO₂ content to be less than or equal to50 ppm. Such specifications are not applied on natural gas streams inpipeline networks, which may involve the CO₂ content up to 2 vol. %based on the total volume of the gaseous feed stream. As such, for LNGfacilities that use the pipeline gas (e.g., natural gas) as the rawfeed, additional treating or processing steps are utilized to furtherpurify the stream. Further, the present techniques may be used to lowerthe water content of the stream to less than 0.1 ppm. Exemplary swingadsorption processes and configurations may include U.S. Patent Ser.Nos. 62/213,262; 62/213,267; 62/213,270; 62/213,273; 62/246,916;62/246,920; and 62/246,922, which are each incorporated by referenceherein.

The present techniques provide configurations and processes that areutilized to enhance the startup mode for the swing adsorption processand associated downstream processes. While the normal operation modeprocesses are described based on steady state operation, startup modeprocedures involve different cycles until normal operation mode isbegun. The present techniques describes different methods that may beutilized to transition the operation from startup mode to normaloperation mode. In startup mode, each of the adsorbent beds utilized inthe swing adsorption process is assumed to be in equilibrium withcontaminants. For dehydration applications, the contaminant is water(H₂O), while for carbon dioxide (CO₂) applications, the contaminant iseither H₂O (e.g., in equilibrium with atmosphere) or CO₂ (e.g., in caseof a shutdown). Accordingly, the startup mode is utilized to removecontaminants to prepare the adsorbent beds for normal operation mode. Inparticular, the startup mode sequence may be used for swing adsorptionprocesses (e.g., dehydration and low-level CO₂ removal) upstream orintegrated with NGL and LNG applications.

The startup mode process may involve the use of an external medium toremove one or more contaminants from the adsorbent beds. In the externalstartup mode, an external medium is used to remove one or morecontaminants from the adsorbent beds. The external medium may includethe use of an external gas stream that is circulated through theadsorbent beds to remove the one or more contaminants from the adsorbentbeds during a regeneration step (e.g., a purge step). The external gasstream may include nitrogen, dry methane or other non-reactive streamunder process operating conditions. For example, the external stream mayinclude predominately nitrogen or methane with less than 0.1 ppm ofwater, less than 1 ppm of water or less than 10 ppm of water. Theexternal gas stream may comprise at least one of nitrogen, methane,helium, hydrogen or any combination thereof.

For example, in dehydration applications, an external gas stream, suchas dry nitrogen (e.g., nitrogen stream having less than 0.1 ppm ofwater, less than 1 ppm of water or less than 10 ppm of water), may beused to remove water from the adsorbent beds during the startup mode.When the dry nitrogen stream is introduced into each of the adsorbentbeds, which is at equilibrium with ambient water, some of the watertransfers from the adsorbent material in the adsorbent bed to the drynitrogen stream. The startup mode sequence may involve providing feed tothe adsorbent bed during an adsorption step and using the externalstream to purge the adsorbent bed during a purge step. The startup modecycle may continue to use the dry nitrogen until a sufficient amount ofwater is removed from each of the adsorbent beds and a desired bedprofile is achieved for the adsorbent beds. Then, the resulting productstream from the adsorbent beds is within the desired specification(e.g., below the specific contaminant levels for the product stream). Inaddition, the startup mode may include maintaining the purge step withdry nitrogen to sufficient amounts of moisture, and then start thesequence described above. In such a configuration, the product streammay be within specification from the first cycle.

Once the product stream is within the desired specification, the productstream may be used in the startup mode process for the downstreamprocesses, such as a demethanizer or a liquefaction train. As thedownstream processes and units are being started, the adsorbent bedscontinue to regenerate using the external gas stream, such as the drynitrogen stream. Alternatively, a heated slip stream from the productside may also be used to regenerate the spent adsorbent beds. As thedownstream process begins producing a purge stream, this purge streammay be combined with the external gas stream and the amount of externalgas stream utilized in the purge step may be adjusted. Once thedownstream processes begin normal operations, the desired purge stream(e.g., within the desired specifications), such as a residue gas streamor fuel gas stream, is provided to the adsorbent bed as part of thenormal operation mode. At this point, the adsorbent bed regenerationstream is transitioned from nitrogen to the purge stream from thedownstream process.

To facilitate rapid regeneration and minimize the amount of dry nitrogenbeing utilized during the external startup mode, the operatingconditions may be adjusted to manage the removal of contaminants fromthe adsorbent bed. For example, the flow rate for the gaseous feedstream may be conducted within a flow rate range below the normaloperation mode flow ranges (e.g., flow rate at turndown). For example,the flow rates in startup mode may be at about 25% of the normaloperation mode flow rate, at about 50% of the normal operation mode flowrate, at about 75% of the normal operation mode flow rate, in a rangebetween 25% and 90% of the normal operation flow rate, in a rangebetween 50% and 90% of the normal operation flow rate, and in a rangebetween 75% and 90% of the normal operation flow rate. Further, theregeneration of the adsorbent bed may be conducted within a pressurerange near atmospheric pressure (e.g., in a pressure range betweenatmospheric pressure and fifty pounds per square inch gauge (psi) aboveatmospheric pressure) or may be within a pressure range near normaloperation mode pressures (e.g., in a pressure range between 75% ofnormal operation mode pressure and 125% of normal operation modepressure or at a pressure between atmospheric pressure and normaloperating pressure or a pressure close to feed pressure). As an example,the regeneration of the adsorbent bed may be conducted in a pressurerange from 300 pounds per square inch gauge (psi) to 650 psi. Also, thetemperature of the external medium stream may be provided within atemperature range from (e.g., in a temperature range between 20° Celsius(C) above atmospheric temperature and 150° Celsius (C) above atmospherictemperature). Also, the temperature of the external stream may be in arange between 350° F. and 550° F., in a range between 350° F. and 550°F. or in a range 450° F. and 550° F. in a range between 100° F. and 550°F., in a range between 150° F. and 450° F. or in a range 250° F. and350° F.

For a dehydration application, the sequence of the cycle for the startupmode may be configured to lessen flaring of gas or completely eliminateflaring of gas. The external sequence may be initiated at turndown. Thepurge pressure is selected such that the purge product is at the suctionpressure of the residue gas compressor. The residue gas compressor isthen operated to compress the purge product and recombine with the feedstream either upstream or downstream of a triethylene glycol (TEG) baseddehydration unit. Knockout drums may be necessary to remove the excesswater gathered from the purge step.

As a specific example, the startup mode process may be used for acryogenic NGL recovery facility. The external startup process mayinclude passing wet gas to the absorbent units at turndown. Then, theexternal startup process is utilized to clean the adsorbent beds. Theprocess is continued until product stream is at specification and thedesired water profile in the adsorbent bed is achieved. Next, the flowrate of the gas stream entering the adsorbent beds is increased forsubsequent cycles. Then, at least a portion of the dry product stream isintroduced to the cryogenic NGL recovery facility. As necessary, thepurge inlet temperature may be adjusted to achieve the necessary purgeto remove the water in the adsorbent beds. With the product stream fromthe adsorbent beds, the startup sequence for the cryogenic NGL recoveryfacility is initiated. This cryogenic NGL facility may perform thestartup mode using the residue gas compressor to recycle thedemethanizer column overhead product with the external stream. Once theNGL recovery facility is approaching specification, a portion of thedemethanizer overhead product is mixed with the purge stream from theadsorbent beds in swing adsorption process to increase the flow rate.The heat from the startup heater may be reduced as necessary.Eventually, the overhead product stream from the demethanizer isintroduced to the adsorbent beds as a purge stream for the respectivecycles and the portion of the external stream from the adsorbent bedbeing used as the purge stream is lessened and may be eliminated. Theprocess eventually transitions to normal operation mode, which is asteady state with the adsorbent beds purge product gas being providedfor sale.

Similarly, the above sequence may be used for the LNG process. However,a source of gas to compress the purge product to feed pressure may notbe available with the LNG process during startup mode. As such, some ofthe purge stream may have to be flared. For the CO₂ removal processes, asimilar external startup mode sequence may be used. Additionally, a loopheating step may be used to provide the necessary heat to the adsorbentbeds.

One or more variants to the procedure noted above may be used to reducethe startup time of the process. The first variant includes heatingadsorbent beds to reduce the amount of water in the adsorbent beds,which may be performed initially. In the heating step, the heated streamat low pressure is used as the purge stream for the absorbent beds andremoves a large amount of water already adsorbed in the adsorbent beds.A second variant involves performing one or more blowdown steps in thestartup mode process to flare or rapidly decrease the partial pressureand reduce the amount of water adsorbed in the adsorbent beds. A thirdvariant involves performing a purge step with dry nitrogen, which may beheated, if necessary, to dry the adsorbent beds.

The present techniques provide a startup mode process that may beutilized to initiate the normal operation mode process for a swingadsorption process, and specifically a rapid cycle adsorption process.The present techniques may include some additional equipment, such asone or more conduits and/or one or more manifolds that provide a fluidpath for the external gas stream, an external gas storage tank, aheating unit (furnace and/or heat exchanger), one or more blowers and/orone or more compressors to fluidly communication with one or moreadsorbent beds, and/or depressurizing equipment that may be utilized tofacilitate the startup mode cycle. In addition, other components andconfigurations may be utilized to provide the swing adsorption process,such as rapid cycle enabling hardware components (e.g., parallel channeladsorbent bed designs, rapid actuating valves, adsorbent bedconfigurations that integrate with other processes). Exemplary swingadsorption processes and configurations may also include U.S. PatentSer. Nos. 62/213,262; 62/213,267; 62/213,270; 62/213,273; 62/246,916;62/246,920; and 62/246,922, which are each incorporated by referenceherein.

In one or more embodiment, a startup mode process for a swing adsorptionprocess may include using an external startup mode. For the externalstartup mode, the present techniques comprise a process for removingcontaminants from a gaseous feed stream with a swing adsorption process,which may be utilized with one or more downstream processes. The processcomprising: a) performing a regeneration step (e.g., purge step),wherein the step comprises passing an external gas stream through anadsorbent bed unit to remove contaminants from an adsorbent bed within ahousing of the adsorbent bed unit to form a purge product stream; b)performing one or more adsorption steps, wherein each of the one or moreadsorption steps comprise passing a gaseous feed stream through anadsorbent bed unit having an adsorbent bed to separate contaminants fromthe gaseous feed stream to form a product stream; c) determining whetherthe product stream is within a specification for at least onecontaminant; d) if the product stream is within the specification (e.g.,is below a certain threshold), passing the product stream to adownstream process; and e) if the product stream is not within thespecification (e.g., above a certain threshold), repeating the steps a)to d) for at least one additional cycle.

As another example for the external startup mode, a cyclical swingadsorption system may include a plurality of manifolds; a plurality ofadsorbent bed units coupled to the plurality of manifolds, and anexternal gas bypass valve in fluid communication with purge manifold andconfigured to provide a flow passage for an external gas stream from anexternal gas storage vessel to the purge manifold in a startup modeposition and configured to block the flow passage of the external gasstream from the external gas storage vessel to the purge manifold in anormal operation mode position. The plurality of manifolds comprise afeed manifold configured to pass a feed stream to the plurality ofadsorbent bed units during an adsorption step, a product manifoldconfigured to pass a product stream from the plurality of adsorbent bedunits during the adsorption step, a purge manifold configured to pass apurge stream to the plurality of adsorbent bed units during aregeneration step, a purge product manifold configured to pass a purgeproduct stream from the plurality of adsorbent bed units during theregeneration step. Each manifold of the plurality of manifolds isassociated with one swing adsorption process step of a plurality ofswing adsorption process steps. Each of the adsorbent bed unitscomprising a housing; an adsorbent material disposed within the housing;a plurality of valves, wherein at least one of the plurality of valvesis associated with one of the plurality of manifolds and is configuredto manage fluid flow along a flow path extending between the respectivemanifold and the adsorbent material.

In addition, the system or method may include certain features toenhance the operation of the system or method. For example, theplurality of valves may comprise one or more poppet valves; theplurality of manifolds and/or the plurality of adsorbent bed units maybe configured to operate at pressures between 0.1 bar absolute (bara)and 100 bara; the system may include a heating unit disposed upstream ofthe purge manifold and downstream of the external gas storage vessel,wherein the heating unit is configured to heat the external gas streamto a temperature in the range between a temperature in the range betweena temperature in the range between 450° F. and the gaseous feed streamtemperature or in the range between 450° F. and greater than 100° F. ofthe gaseous feed stream temperature; the system may include aconditioning unit disposed downstream of the purge product manifold andupstream of the external gas storage vessel, wherein the conditioningunit is configured to remove one or more contaminants from the purgeproduct stream; the plurality of manifolds may further comprise ablowdown manifold configured to pass a blowdown stream from theplurality of adsorbent bed units during a blowdown step; and the systemmay include a liquefied natural gas process unit in fluid communicationwith the adsorbent bed unit and configured to receive the product streamand separate the product stream into a final product stream and a flashfuel stream, wherein the flash fuel stream is passed to the purgemanifold. Further, the external gas stream comprises a nitrogen streamcomprising predominately nitrogen with less than 0.1 ppm of water, ormay comprise a nitrogen stream comprising predominately nitrogen withless than 10 ppm of water. The external gas stream may be a nitrogencontaining stream having greater than one volume percent nitrogen basedon the total volume of the feed stream. Also, the method may includemixing a slip stream from the downstream process with the external gasstream prior to performing the purge step and/or adjusting the amount ofexternal gas stream utilized in the performing a purge step based on theamount of the slip stream from the downstream process. The slip streammay be an overhead stream, such as overhead stream from NGL or fuel fromLNG.

In other certain embodiments, the startup mode for the swing adsorptionprocess may be integrated with downstream equipment and processes. Thedownstream equipment and processes may include control freeze zone (CFZ)applications, nitrogen removal unit (NRU), cryogenic NGL recoveryapplications, LNG applications, and other such applications. Each ofthese different applications may include different specifications forthe feed stream in the respective process. For example, the startupprocess may involve dehydration upstream of a cryogenic NGL process oran LNG process and may be integrated with the respective downstreamequipment. As another example, the startup process may involve CO₂removal upstream of a cryogenic NGL process or the LNG process and maybe integrated with respective downstream equipment. The startup methodmay include using an external medium as part of the process, which maybe a dry nitrogen stream. Further, the startup mode may be integratedwith downstream processes, such as cryogenic NGL processes and/or LNGprocesses. In addition, the startup mode process may involve performingthe startup mode cycle with minimal flaring or no flaring.

In certain embodiments, the system utilizes a combined swing adsorptionprocess, which combines TSA and PSA, for treating of pipeline qualitynatural gas to remove contaminants for the stream to satisfy LNGspecifications. The swing adsorption process, which may be a rapid cycleprocess, is used to treat natural gas that is at pipeline specifications(e.g., a feed stream of predominately hydrocarbons along with less thanor equal to about 2% volume CO₂ and/or less than or equal to 4 ppm H₂S)to form a stream satisfying the LNG specifications (e.g., less than 50ppm CO₂ and less than about 4 ppm H₂S). The product stream, which may bethe LNG feed stream, may have greater than 98 volume percenthydrocarbons based on the total volume of the product stream, while theCO₂ and water content are below certain thresholds. The LNGspecifications and cryogenic NGL specifications may involve the CO₂content to be less than or equal to 50 ppm, while the water content ofthe stream may be less than 0.1 ppm. Further, the gaseous feed streammay include hydrocarbons and H₂O. For example, the gaseous feed streammay be that the H₂O is in the range of 0.2 parts per million volume tosaturation levels in the gaseous feed stream or the H₂O is in the rangeof 100 parts per million volume to 1500 parts per million volume.

In certain aspects, as described further below, the present techniquesmay involve using a high temperature stream that is provided to theadsorbent beds as part of the purge step to heat the adsorbent bed. Thestream, which may be referred to as the purge stream (e.g., the externalstream), may be heated to temperature may be less than 550° F., may beless than 500° F., less than 450° F. or may be less than 350° F., andmay be greater than 50° F. of the gaseous feed stream temperature,greater than 100° F. of the gaseous feed stream temperature or greaterthan 250° F. of the gaseous feed stream temperature. For example, thestream used during the purge step of the startup mode cycle may be atemperature in the range between 500° F. and greater than 50° F. of thegaseous feed stream temperature, in the range between 450° F. and thegaseous feed stream temperature, in the range between a temperature inthe range between 450° F. and greater than 100° F. of the gaseous feedstream temperature or 400° F. and greater than 200° F. of the gaseousfeed stream temperature. The stream (purge stream or external stream)pressure may be in the range between 0.01 bara and 100 bara, between 1bara and 80 bara, or between 2 bara and 50 bara.

Further, the present techniques may not remove all of the contaminant(e.g., H₂O and CO₂) adsorbed in the bed during the purge step of thestartup mode process, but remove a portion of the contaminants such thatthe product end of the adsorbent bed has a contaminant loadingsufficiently low to provide a product stream with less thanspecifications. Accordingly, the product end of the adsorbent bed may bemaintained nearly free of contaminants (e.g., the CO₂ loading for theregion near the product end is less than 1 millimole per gram (mmol/g),less than 0.5 mmol/g or less than 0.1 mmol/g). The loading level ofcontaminant may be lower on the feed side of the adsorbent bed duringthe purge step, but the length of adsorbent bed that containscontaminants is reduced during the purge step. For example, a feedregion may be a specific portion of the adsorbent bed from the feed endof the adsorbent bed to 10% of the bed length, from the feed end of theadsorbent bed to 25% of the bed length or from the feed end of theadsorbent bed to 40% of the bed length. The product region may be aspecific portion of the adsorbent bed from the product end of theadsorbent bed to 10% of the bed length, from the product end of theadsorbent bed to 25% of the bed length or from the product end of theadsorbent bed to 40% of the bed length. The movement of the contaminantsfront back during purge step and forward during the adsorption step isthe basis of the swing capacity of the process. In part, this isachieved by using a limited, cost effective quantity of purge gas in thepurge steam along with the heating of the adsorbent bed in this processand configuration.

The present techniques may involve using two or more adsorbent beds,which are operated on similar cycle that are performing different stepsof the cycles (e.g., not synchronized with each other) to maintain asteady flow of fluids for the various streams (e.g., feed stream,product stream, heating stream, and purge stream).

Further, in other embodiments, the pressure of the different streams maybe varied. For example, the feed stream may involve a feed pressure thatis within the in the range between 0.01 bara and 100 bara, between 1bara and 80 bara, or between 2 bara and 50 bara, but is not necessarilylimited to this range. The feed temperature may be in the range between0° F. and 200° F., in the range between 20° F. and 175° F. or in therange between 40° F. and 150° F. The blowdown pressure, heatingpressure, and purge pressure may be adjusted depending on the cycle, maydepend upon the adsorbent material being utilized and/or may range fromvacuum to feed pressure. For example, if the adsorbent material iszeolite 4A, the blowdown pressure range may be between 0.01 bara to 50bara, or more preferably in a range between 1 bara and 15 bara. Thisexample may depend on the feed concentration of CO₂. Also, in otherembodiments, the depressurization steps may be adjusted such that thepressure swing is achieved in stages to vary the amount of methanedesorbing during each step, if any. Additionally, a heating loop may beintroduced and the heating pressure in the heating loop may be operatedat a pressure different from the purge pressure or blowdown pressure inthe respective steps. Also, certain embodiments may include no pressureswing, but may rely upon temperature swing for the regeneration step.Similarly, in the other embodiments, no temperature swing may beperformed and the regeneration step may be performed by pressure swing.

Furthermore, the above process may be used for startup mode processesthat separate two or more contaminants from the feed stream (e.g., twoswing adsorption processes operated in series with each other). Forexample, the feed stream may subjected to a dehydration swing adsorptionprocess, then a CO₂ removal swing adsorption process, and the resultingproduct may be subjected to a downstream process, such as cryogenic NGLor LNG recovery. The startup mode for the dehydration and the CO₂removal processes may involve external startup processes. As oneexample, the dehydration process may involve the external startupprocess. Then, once the product stream satisfies the desiredspecification for water removal, the product stream may be used by theCO₂ removal as part of the external startup stream. Alternatively, thedehydration process may involve the external startup process and the CO₂removal process may perform another external startup mode process andmay mix the purge stream with the feed stream to the dehydrationprocess.

In certain configurations, an integrated rapid cycle adsorption systemmay be utilized to remove multiple contaminants (e.g., water and CO₂).Suitable adsorbent material or adsorbent layers may be utilized toprovide the dehydration, which may be the same or different from theadsorbent material used to in the removal of other contaminants, such asCO₂.

Moreover, the present techniques may include a specific process flowduring normal operation mode to remove contaminants, such as CO₂ and/orwater. For example, the process may include an adsorbent step and aregeneration step, which form the cycle. The adsorbent step may includepassing a gaseous feed stream at a feed pressure and feed temperaturethrough an adsorbent bed unit to separate one or more contaminants fromthe gaseous feed stream to form a product stream. The feed stream may bepassed through the adsorbent bed in a forward direction (e.g., from thefeed end of the adsorbent bed to the product end of the adsorbent bed).Then, the flow of the gaseous feed stream may be interrupted for aregeneration step. The regeneration step may include one or moredepressurization steps, one or more heating steps, and/or one or morepurge steps. The depressurization steps, which may be or include ablowdown step, may include reducing the pressure of the adsorbent bedunit by a predetermined amount for each successive depressurizationstep, which may be a single step and/or multiple steps. Thedepressurization step may be provided in a forward direction or maypreferably be provided in a countercurrent direction (e.g., from theproduct end of the adsorbent bed to the feed end of the adsorbent bed).The heating step may include passing a heating stream into the adsorbentbed unit, which may be a recycled stream through the heating loop and isused to heat the adsorbent material. The purge step may include passinga purge stream into the adsorbent bed unit, which may be a once throughpurge step and the purge stream may be provided in countercurrent flowrelative to the feed stream. The purge stream may be provided at a purgetemperature and purge pressure, which may include the purge temperatureand purge pressure being similar to the heating temperature and heatingpressure used in the heating step. Then, the cycle may be repeated foradditional streams. Additionally, the process may include one or morere-pressurization steps after the purge step and prior to the adsorptionstep. The one or more re-pressurization steps may be performed, whereinthe pressure within the adsorbent bed unit is increased with eachre-pressurization step by a predetermined amount with each successivere-pressurization step. The cycle duration for normal operation mode maybe for a period greater than 1 second and less than 600 seconds, for aperiod greater than 2 second and less than 300 seconds, for a periodgreater than 2 second and less than 180 seconds, for a period greaterthan 5 second and less than 150 seconds or for a period greater than 5second and less than 90 seconds.

In other configurations, the startup mode may involve lower flow ratesand longer cycles. For example, the initial flow rate may be 25% of thenormal flow rate utilized during normal operations, which may have astartup mode cycle time of four times the normal operation model cycletime. This initial flow rate may be increased in a steady manner or invarious increments until the normal operation mode is reached. By way ofexample, the startup mode cycle duration may be for a period greaterthan 1 second and less than 2400 seconds, for a period greater than 1second and less than 1500 seconds, for a period greater than 1 secondand less than 600 seconds, for a period greater than 2 second and lessthan 800 seconds, for a period greater than 2 second and less than 400seconds, for a period greater than 5 second and less than 150 seconds orfor a period greater than 5 second and less than 90 seconds.

In yet other configurations, the startup mode may involve installationof adsorbent beds that are partially or completely devoid of thecontaminant being removed. By way of example, if the swing adsorptionprocess is primarily configured to remove water, then a partially ortotally dehydrated adsorbent bed may be installed in the system. Duringthe start mode, a feed stream is passed to the adsorbent bed, which maybe as a wet gas, and a product stream, which may be a dry stream, isconducted away and may be used as a purge stream to a differentadsorbent bed. Alternatively, another method may involve installation ofan adsorbent bed in the swing adsorption process that is treated orconditioned such that the contaminant replaces a different molecule thatis already adsorbed on the adsorbent bed. By way of example, if theswing adsorption process is primarily configured to remove CO₂, then theadsorbent bed may include adsorbed particles, such as water, which maybe installed in the system. During the start mode, a feed stream ispassed to the adsorbent bed, which may include the CO₂ contaminants, anda product stream may be conducted away and may be used as a purge streamto a different adsorbent bed.

In certain configurations, a process for removing contaminants from agaseous feed stream with a swing adsorption process is described. Theprocess comprising: a) performing a purge step, wherein the purge stepcomprises passing an external gas stream through an adsorbent bed unitto remove one or more contaminants from an adsorbent bed within ahousing of the adsorbent bed unit to form a purge product stream; b)performing one or more adsorption steps, wherein each of the one or moreadsorption steps comprise passing a gaseous feed stream through anadsorbent bed unit having an adsorbent bed to separate one or morecontaminants from the gaseous feed stream to form a product stream; c)determining whether the product stream is within a specification for acontaminant; d) if the product stream is within the specification,passing the product stream to a downstream process; and e) if theproduct stream is not within the specification, repeating the steps a)to d) for at least one additional cycle.

The process may include various configuration changes to enhance theoperations. For example, the process may further comprising mixing aslip stream from the downstream process with the external gas streamprior to performing the purge step; adjusting the amount of external gasstream utilized in the performing a purge step based on the amount ofthe slip stream from the downstream process; heating the external gasstream prior to passing the external gas stream through an adsorbent bedunit; wherein the external gas stream is heated to a temperature in therange between 500° F. and greater than 50° F. of the gaseous feed streamtemperature or to a temperature in the range between 450° F. and thegaseous feed stream temperature; heating the purge product stream,wherein the purge product stream is heated to a temperature 10° F.greater than the dew point of the purge product stream; separating oneor more contaminants from the purge product stream to form conditionedpurge product stream and mixing the conditioned purge product streamwith external gas source stream to form the external gas stream; whereinthe purge stream is passed in a countercurrent direction relative to thedirection of the feed stream and wherein a temperature differentialexists at the end of the purge step in a range between 100° F. and 400°F., wherein the temperature differential is the difference intemperatures between a feed end of the adsorbent bed and a product endof the adsorbent bed; wherein the cycle duration is for a period greaterthan 1 second and less than 2400 seconds or is greater than 2 secondsand less than 800 seconds; wherein the gaseous feed stream is ahydrocarbon containing stream having greater than one volume percenthydrocarbons based on the total volume of the feed stream; wherein thegaseous feed stream comprises hydrocarbons and CO₂, wherein the CO₂content is in the range of two hundred parts per million volume and lessthan or equal to about 2% volume of the gaseous feed stream; wherein theadsorbent bed unit is configured to lower the carbon dioxide (CO₂) levelto less than 50 parts per million; wherein the gaseous feed streamcomprises hydrocarbons and H₂O, wherein the H₂O is in the range of 0.2parts per million volume to saturation levels in the gaseous feedstream; wherein the gaseous feed stream comprises hydrocarbons and H₂O,wherein the H₂O is in the range of 100 parts per million volume to 1500parts per million volume; passing the product stream from the adsorbentbed unit to a liquefied natural gas (LNG) process unit and separating aflash fuel stream from the LNG process unit to be utilized as at least aportion of the purge stream; passing the product stream from theadsorbent bed unit to a cryogenic natural gas liquid recovery (NGL)process unit and separating an overhead stream from the NGL process unitto be utilized as at least a portion of the purge stream; wherein theexternal gas stream is a nitrogen containing stream having greater thanone volume percent nitrogen based on the total volume of the feedstream; wherein the external gas stream comprises a predominatelynitrogen stream comprising less than 0.1 ppm of water or less than 10ppm of water; and/or wherein the external gas stream comprises at leastone of nitrogen, methane, helium, hydrogen or any combination thereof.

In yet other configurations, a cyclical swing adsorption system isdescribed. The system may include: a plurality of manifolds, wherein theplurality of manifolds comprise a feed manifold configured to pass afeed stream to the plurality of adsorbent bed units during an adsorptionstep, a product manifold configured to pass a product stream from theplurality of adsorbent bed units during the adsorption step, a purgemanifold configured to pass a purge stream to the plurality of adsorbentbed units during a regeneration step, a purge product manifoldconfigured to pass a purge product stream from the plurality ofadsorbent bed units during the regeneration step, each manifold of theplurality of manifolds is associated with one swing adsorption processstep of a plurality of swing adsorption process steps; a plurality ofadsorbent bed units coupled to the plurality of manifolds, each of theadsorbent bed units comprising: a housing; an adsorbent materialdisposed within the housing; a plurality of valves, wherein at least oneof the plurality of valves is associated with one of the plurality ofmanifolds and is configured to manage fluid flow along a flow pathextending between the respective manifold and the adsorbent material; anexternal gas bypass valve in fluid communication with purge manifold andconfigured to provide a flow passage for an external gas stream from anexternal gas storage vessel to the purge manifold in a startup modeposition and configured to block the flow passage of the external gasstream from the external gas storage vessel to the purge manifold in anormal operation mode position.

The system may include various configuration changes to enhance theoperations. For example, the cyclical swing adsorption system mayinclude that the plurality of valves comprise one or more poppet valves;may include that the plurality of adsorbent bed units are configured tooperate at pressures between 0.1 bar absolute (bara) and 100 bara; mayfurther include a heating unit disposed upstream of the purge manifoldand downstream of the external gas storage vessel, wherein the heatingunit is configured to heat the external gas stream to a temperature inthe range between a temperature in the range between 450° F. and thegaseous feed stream temperature; may further include a conditioning unitdisposed downstream of the purge product manifold and upstream of theexternal gas storage vessel, wherein the conditioning unit is configuredto remove one or more contaminants from the purge product stream; mayinclude that the plurality of manifolds further comprise a blowdownmanifold configured to pass a blowdown stream from the plurality ofadsorbent bed units during a blowdown step; may further include aliquefied natural gas process unit in fluid communication with theadsorbent bed unit and configured to receive the product stream andseparate the product stream into a final product stream and a flash fuelstream, wherein the flash fuel stream is passed to the purge manifold;may further comprising a cryogenic natural gas liquid recovery (NGL)process unit in fluid communication with the adsorbent bed unit andconfigured to receive the product stream and separate the product streaminto a final product stream and a residue gas stream, wherein theresidue gas stream is passed to the purge manifold; and/or may furtherinclude a heating jacket disposed adjacent to the adsorbent bed unit andconfigured to heat the adsorbent bed.

In one or more embodiments, the present techniques can be used for anytype of swing adsorption process. Non-limiting swing adsorptionprocesses for which the present techniques may be used include pressureswing adsorption (PSA), vacuum pressure swing adsorption (VPSA),temperature swing adsorption (TSA), partial pressure swing adsorption(PPSA), rapid cycle pressure swing adsorption (RCPSA), rapid cyclethermal swing adsorption (RCTSA), rapid cycle partial pressure swingadsorption (RCPPSA), as well as combinations of these processes. Forexample, the preferred swing adsorption process may include a combinedpressure swing adsorption and temperature swing adsorption, which may beperformed as a rapid cycle process. Exemplary swing adsorption processesare further described in U.S. Patent Ser. Nos. 62/213,262; 62/213,267;62/213,270; 62/213,273; 62/246,916; 62/246,920; and 62/246,922 and U.S.Patent Application Publication Nos. 2008/0282892, 2008/0282887,2008/0282886, 2008/0282885, 2008/0282884 and 20140013955, which are eachherein incorporated by reference in their entirety.

Further still, in one or more embodiments, a variety of adsorbentmaterials may be used to provide the mechanism for the separations.Examples include zeolite 3A, 4A, 5A, ZK4 and MOF-74. However, theprocess is not limited to these adsorbent materials, and others may beused as well. The present techniques may be further understood withreference to the FIGS. 1 to 9 below.

FIG. 1 is a three-dimensional diagram of the swing adsorption system 100having six adsorbent bed units and interconnecting piping. While thisconfiguration is a specific example, the present techniques broadlyrelate to adsorbent bed units that can be deployed in a symmetricalorientation, or non-symmetrical orientation and/or combination of aplurality of hardware skids. Further, this specific configuration is forexemplary purposes as other configurations may include different numbersof adsorbent bed units.

In this system, the adsorbent bed units, such as adsorbent bed unit 102,may be configured for a cyclical swing adsorption process for removingcontaminants from feed streams (e.g., fluids, gaseous or liquids). Forexample, the adsorbent bed unit 102 may include various conduits (e.g.,conduit 104) for managing the flow of fluids through, to or from theadsorbent bed within the adsorbent bed unit 102. These conduits from theadsorbent bed units 102 may be coupled to a manifold (e.g., manifold106) to distribute the flow to, from or between components. Theadsorbent bed within an adsorbent bed unit may separate one or morecontaminants from the feed stream to form a product stream. As may beappreciated, the adsorbent bed units may include other conduits tocontrol other fluid steams as part of the process, such as purgestreams, depressurizations streams, and the like. In particular, theadsorbent bed units may include startup mode equipment, such as one ormore heating units (not shown), one or more external gas sourcemanifolds, which may be one of the manifolds 106) and one or moreexpanders, as noted further below, which is used as part of the startupmode for the adsorbent beds. Further, the adsorbent bed unit may alsoinclude one or more equalization vessels, such as equalization vessel108, which are dedicated to the adsorbent bed unit and may be dedicatedto one or more step in the swing adsorption process. The equalizationvessel 108 may be used to store the external stream, such as nitrogenfor use in the startup mode cycle.

As an example, which is discussed further below in FIG. 2, the adsorbentbed unit 102 may include a housing, which may include a head portion andother body portions, that forms a substantially gas impermeablepartition, an adsorbent bed disposed within the housing and a pluralityof valves (e.g., poppet valves) providing fluid flow passages throughopenings in the housing between the interior region of the housing andlocations external to the interior region of the housing. Each of thepoppet valves may include a disk element that is seatable within thehead or a disk element that is seatable within a separate valve seatinserted within the head (not shown). The configuration of the poppetvalves may be any variety of valve patterns or configuration of types ofpoppet valves. As an example, the adsorbent bed unit may include one ormore poppet valves, each in flow communication with a different conduitassociated with different streams. The poppet valves may provide fluidcommunication between the adsorbent bed and one of the respectiveconduits, manifolds or headers. The term “in direct flow communication”or “in direct fluid communication” means in direct flow communicationwithout intervening valves or other closure means for obstructing flow.As may be appreciated, other variations may also be envisioned withinthe scope of the present techniques.

The adsorbent bed comprises a solid adsorbent material capable ofadsorbing one or more components from the feed stream. Such solidadsorbent materials are selected to be durable against the physical andchemical conditions within the adsorbent bed unit 102 and can includemetallic, ceramic, or other materials, depending on the adsorptionprocess. Further examples of adsorbent materials are noted furtherbelow.

FIG. 2 is a diagram of a portion of an adsorbent bed unit 200 havingvalve assemblies and manifolds in accordance with an embodiment of thepresent techniques. The portion of the adsorbent bed unit 200, which maybe a portion of the adsorbent bed unit 102 of FIG. 1, includes a housingor body, which may include a cylindrical wall 214 and cylindricalinsulation layer 216 along with an upper head 218 and a lower head 220.An adsorbent bed 210 is disposed between an upper head 218 and a lowerhead 220 and the insulation layer 216, resulting in an upper open zone,and lower open zone, which open zones are comprised substantially ofopen flow path volume. Such open flow path volume in adsorbent bed unitcontains gas that has to be managed for the various steps. The housingmay be configured to maintain a pressure from 0 bara (bar absolute) to150 bara within the interior region.

The upper head 218 and lower head 220 contain openings in which valvestructures can be inserted, such as valve assemblies 222 to 240,respectively (e.g., poppet valves). The upper or lower open flow pathvolume between the respective head 218 or 220 and adsorbent bed 210 canalso contain distribution lines (not shown) which directly introducefluids into the adsorbent bed 210. The upper head 218 contains variousopenings (not show) to provide flow passages through the inlet manifolds242 and 244 and the outlet manifolds 248, 250 and 252, while the lowerhead 220 contains various openings (not shown) to provide flow passagesthrough the inlet manifold 254 and the outlet manifolds 256, 258 and260. Disposed in fluid communication with the respective manifolds 242to 260 are the valve assemblies 222 to 240. If the valve assemblies 222to 240 are poppet valves, each may include a disk element connected to astem element which can be positioned within a bushing or valve guide.The stem element may be connected to an actuating means, such asactuating means (not shown), which is configured to have the respectivevalve impart linear motion to the respective stem. As may beappreciated, the actuating means may be operated independently fordifferent steps in the process to activate a single valve or a singleactuating means may be utilized to control two or more valves. Further,while the openings may be substantially similar in size, the openingsand inlet valves for inlet manifolds may have a smaller diameter thanthose for outlet manifolds, given that the gas volumes passing throughthe inlets may tend to be lower than product volumes passing through theoutlets.

In swing adsorption processes, the cycle involves two or more steps thateach has a certain time interval, which are summed together to be thecycle time or cycle duration. These steps include regeneration of theadsorbent bed following the adsorption step using a variety of methodsincluding pressure swing, vacuum swing, temperature swing, purging (viaany suitable type of purge fluid for the process), and combinationsthereof. As an example, a PSA cycle may include the steps of adsorption,depressurization, purging, and re-pressurization. When performing theseparation at high pressure, depressurization and re-pressurization(which may be referred to as equalization) may be performed in multiplesteps to reduce the pressure change for each step and enhanceefficiency. In some swing adsorption processes, such as rapid cycleswing adsorption processes, a substantial portion of the total cycletime is involved in the regeneration of the adsorbent bed. Accordingly,any reductions in the amount of time for regeneration results in areduction of the total cycle time. This reduction may also reduce theoverall size of the swing adsorption system.

Further, in startup mode for the swing adsorption process, one or moreof the manifolds and associated valves may be utilized as a dedicatedflow path for one or more startup streams. For example, during theadsorption or feed step, the manifold 242 and valve assembly 222 may beutilized to pass the feed gas stream to the adsorbent bed 210, while thevalve assembly 236 and manifold 256 may be used to conduct away theproduct stream from the adsorbent bed 210. During the regeneration orpurge step, the manifold 244 and valve assembly 224 may be utilized topass the external gas stream to the adsorbent bed 210, while the valveassembly 236 and manifold 256 may be used to conduct away the purgeproduct stream from the adsorbent bed 210. Accordingly, the manifold 244and valve assembly 224 may be utilized for startup mode processes, butremain inactive during normal operation mode. As may be appreciated, thepurge stream may be configured to flow counter current to the feedstream in other embodiments.

Alternatively, the startup mode for the swing adsorption process mayinvolve sharing one or more of the manifolds and associated valvesduring the normal operation mode and during startup mode. For example,the manifold 242 and valve assembly 222 may be utilized to feed thegaseous feed stream to the adsorbent bed 210 during startup mode andduring normal operations, while the valve assembly 236 and manifold 256may be used to conduct away the product stream from the adsorbent bed210 may be used to conduct away the product stream during startup modeand during normal operation mode. During the regeneration or purge step,the manifold 254 and valve assembly 232 may be utilized to pass theexternal gas stream to the adsorbent bed 210 for startup mode and topass the purge stream to the adsorbent bed 210 for normal operationmode, while the valve assembly 226 and manifold 248 may be used toconduct away the purge product stream from the adsorbent bed 210 duringstartup mode and normal operation mode. Beneficially, this configurationmay be utilized to lessen any additional valves or connections forstartup mode for adsorbent bed unit configurations that are subject tospace limitations on the respective heads.

During normal operation mode, a gaseous feed stream may be subject tovarious processes to form a NGL stream or a LNG stream. For example, theprocess may include a mercury removal unit to remove mercury from aninput stream; a filter to remove both particular and liquid droplets; aswing adsorption unit to remove one or more contaminants, such as H₂O,CO₂ and sulfur containing species; a LNG process unit or NGL processunit to process the resulting stream into a final product that may beused for sales, shipment or storage. In addition, the configuration mayinclude one or more of a heating loop, a compressor, a heating unitand/or a storage vessel.

As noted above, the present techniques include various procedures thatmay be utilized for the startup mode of the swing adsorption process.The startup mode may include an external startup mode. The externalstartup mode may include performing an adsorption step and then aregeneration step for each of the adsorbent beds. The adsorption stepmay include passing a gaseous feed stream through the adsorbent bed toadsorb one or more contaminants from the gaseous feed stream andconducting away the resulting product stream from the adsorbent bedunit. The resulting product stream may be passed to downstreamprocessing equipment. The regeneration step may include passing anexternal stream through the adsorbent bed to remove one or morecontaminants from the adsorbent bed unit (e.g., a portion of thecontaminants within the adsorbent bed unit or within the voids of theadsorbent bed) and conduct away the purge product stream from theadsorbent bed unit. The purge product stream may be set to flare or maybe combined with fuel gas.

As an example, FIG. 3 is an exemplary flow chart for performing anexternal startup mode of a swing adsorption process in accordance withan embodiment of the present techniques. In this flow chart 300, thestartup mode process may involve the use of an external gas stream toremove one or more contaminants from the adsorbent beds as part of thestartup mode cycle. Further, the startup mode process may includeoperating two or more adsorbent bed units, which may each be performingdifferent steps in the startup mode cycle. For each of the adsorbent bedunits, the swing adsorption process involves a startup mode processusing an external stream, as shown in blocks 302 to 308, which isdescribed as being performed for a single adsorbent bed unit forsimplicity. Then, the adsorbent bed units may be used with thedownstream equipment, as shown in blocks 310 to 316, and normaloperations mode are begun, as shown in block 318. The external gasstream may include nitrogen and/or methane, as noted above. The externalstream may comprise predominately nitrogen and/or methane with less than0.1 ppm of water, or less than 10 ppm of water. The external gas streammay be a nitrogen containing stream having greater than one volumepercent nitrogen based on the total volume of the feed stream.

The process begins by performing the startup mode process for theadsorbent bed units of the swing adsorption process, as shown in blocks302 to 308. At block 302, a regeneration step is performed for theadsorbent bed with an external stream. The external stream may includenitrogen or methane and may be a dry stream (e.g., less than 10 ppm ofwater, less than 1 ppm of water, or less than 0.1 ppm of water). Theregeneration step, which may be one or more purge steps may includepassing the external stream through the adsorbent bed to create a purgeproduct stream that is conducted away from the adsorbent bed unit. Theproduct purge stream may include the external stream and a portion ofthe contaminants within the adsorbent bed. This product purge stream maybe intermingled with a fuel gas stream or may be flared. Further, theexternal stream may be subjected to a heating step prior to being passedto the adsorbent bed. The heating step may heat the external stream to atemperature less than 550° F., less than 500° F., less than 450° F. orless than 350° F., and may be greater than 50° F. of the gaseous feedstream temperature, greater than 100° F. of the gaseous feed streamtemperature or greater than 250° F. of the gaseous feed streamtemperature. For example, the external stream used during the purge stepmay be a temperature in the range between 500° F. and greater than 50°F. of the gaseous feed stream temperature, in the range between atemperature in the range between 450° F. and greater than 100° F. of thegaseous feed stream temperature, in the range between 450° F. and thegaseous feed stream temperature or 400° F. and greater than 200° F. ofthe gaseous feed stream temperature. The heating of the external streammay include passing the stream through a heat exchanger or similarheating unit to increase the temperature of the external stream. Atblock 304, an adsorption step is performed for the adsorbent bed. Theadsorption step may include passing a gaseous feed stream through theadsorbent bed to remove one or more contaminants from the gaseous feedstream and to create a product stream that is conducted away from theadsorbent bed unit. At block 306, the product stream may be measured.The product stream may be measured by taking samples, using a moistureanalyzer, using a gas chromatograph or using another gas componentanalysis equipment. Then, at block 308, a determination may be madewhether the product stream is within specification. This determinationmay include analyzing the product stream to determine the level of oneor more of the contaminants within the product stream. If the productstream is within specification (e.g., contaminants are at or below aspecific threshold), the product stream may be passed to downstreamprocesses. However, if the product stream is not within specifications(e.g., contaminants are above a specific threshold), the product streammay be recycled to be intermingled with the gaseous feed stream andutilized as part of the adsorption step, as shown in block 304.

Once the adsorbent bed units are passing the product stream to thedownstream process, the product stream may be used with the downstreamequipment, as shown in blocks 310 to 316. At block 310, the startup modefor the downstream equipment may begin. The startup mode for thedownstream equipment may involve various steps prior to the passing ofproduct stream to the downstream equipment or may begin once the productstream is passed to the downstream equipment. The downstream processesmay include a CFZ process, a cryogenic NGL recovery process, or an LNGprocess, with the associated equipment for each. Further, during thedownstream startup mode sequence, the adsorbent bed units may continueto utilize the external stream for the purge step. At block 312, a purgestream may be passed to the adsorbent bed units from the downstreamprocess. The purge stream may include an overhead stream or a slipstream from the downstream process. By way of example, the purge streamfrom an NGL facility may be the demethanizer overhead, or the purgestream may be a fuel gas stream for an LNG facility. Then, at block 314,the amount of external stream utilized in the purge step may beadjusted. The adjustment may be based on the amount of the purge streambeing provided to the adsorbent bed units. For example, the flow rate ofthe external stream may be lowered by 10%, 50%, or 90% based on theamount of purge stream from the downstream processes and the desiredflow rate. At block 316, the flow of the external stream may beinterrupted. The flow of the external stream may be interrupted once thedownstream process is producing a sufficient amount of purge stream atconditions close to steady operating conditions.

Once the startup mode process is complete, the normal operation mode maybegin, as shown in block 318. At block 318, normal operation mode isbegun. The normal operation mode may include passing the gaseous feedstream is passed to the adsorbent bed units for the swing adsorptionprocess to remove contaminants and pass the product stream to thedownstream process. Then, the downstream process may pass the productstream through the various downstream equipment to produce a finalproduct stream. The downstream process may also pass a purge stream tothe swing adsorption process, which may be utilized during theregeneration step to remove contaminants from the adsorbent beds withinthe adsorbent bed units.

As a specific example, the feed stream may be a natural gas stream thatpredominately contains hydrocarbons, the external stream may be anitrogen stream and the contaminants within the adsorbent bed may bewater. During the purge step for the respective adsorbent bed, thenitrogen stream is passed through the adsorbent bed and water interactswith the nitrogen stream to form the purge product stream, whichincludes the nitrogen and the portion of the water removed from theadsorbent bed.

In addition, the product stream from the adsorbent bed units may beutilized in the startup mode process for one or more downstream units,such as a demethanizer or a liquefaction train. As the downstreamprocesses and units are being started, the spent adsorbent beds may beregenerated using the dry nitrogen stream as the purge stream. The drynitrogen stream may be heated. Alternatively, a heated slip stream fromthe product side may also be used to regenerate the adsorbent bedsduring the purge step. Once the downstream processes begin normaloperation mode, the purge stream may be adjusted to be provided from aresidue gas stream, a fuel gas stream or other suitable stream from oneof the downstream processes.

In certain embodiments, the purge product stream may be subjected toprocesses to remove the contaminants from the external stream, such thatthe cleaned purge product stream may be recycled to the adsorbent bedunits as the external stream or intermingled with the external stream.For example, if the external stream is a nitrogen stream and thecontaminant is water, the purge product stream may be heated and thenmay be subjected to a pressure drop to separate the water from thenitrogen in the purge product stream. In this manner, the nitrogen maybe regenerated and recycled to the adsorbent beds to remove additionalwater from the adsorbent beds during a subsequent purge step.

As further enhancements, the operating conditions may be adjusted duringthe external startup mode to manage the removal of contaminants from theadsorbent beds. By way of example, flow rate may be in a range between25 and 1000 million standard cubic feet per day (MSCFD) during normaloperation mode, while the flow rate may be in the range between 6.25 and500 MSCFD for startup mode. The flow rate may be increased duringsubsequent purge steps until normal operation mode flow rates arereached. Also, the pressure range of the external stream may be in apressure range between atmospheric pressure and fifty psi aboveatmospheric pressure. In addition, the temperature of the externalstream may be within a temperature range between 20° Celsius (C) aboveatmospheric temperature and 150° C. above atmospheric temperature.Further, the temperature of the external stream may be less than 550°F., less than 500° F., less than 450° F. or less than 350° F., and maybe the gaseous feed stream temperature, greater than 50° F. of thegaseous feed stream temperature, greater than 100° F. of the gaseousfeed stream temperature or greater than 250° F. of the gaseous feedstream temperature. For example, the external stream used during thepurge step may be a temperature in the range between 500° F. and greaterthan 50° F. of the gaseous feed stream temperature, in the range betweena temperature in the range between 450° F. and the gaseous feed streamtemperature; in the range between 450° F. and greater than 100° F. ofthe gaseous feed stream temperature or 400° F. and greater than 200° F.of the gaseous feed stream temperature.

To support the external startup mode process, a configuration of theswing adsorption process may include additional bypass conduits andmanifold to pass the external stream to the adsorbent bed units duringthe purge step. The external stream may be provided from an externalsource vessel through an external source conduit that is in fluidcommunication with purge manifold. In addition, the configuration mayinclude one or more heating units that are upstream of the purgemanifold and configured to heat the external stream prior to passingthrough the adsorbent bed units and/or that are downstream of the purgeproduct manifold and configured to heat the purge product stream. Theheating unit may include a heat exchanger, a furnace, or the like. Theconfiguration may also include one or more separation units configuredto separate one or more contaminants from the purge product stream. Theseparation units may be a flash separation vessel that is configured tolower the pressure of the stream to separate the contaminants from theremaining portion of the purge product stream or may be an adsorptionunit that interacts with the contaminants to separates the contaminantsfrom the remaining portion of the purge product stream. The contaminantsmay be conducted away from the process, while the remaining portion ofthe purge product stream may be passed to one or more regenerationunits. The regeneration units may be utilized to further purify theremaining portion of the purge product stream and/or compress theremaining portion of the purge product stream to form the externalstream that is passed to the adsorbent beds.

In certain embodiments, the external stream may be further conditionedprior to being provided to a subsequent adsorbent bed unit during itsregeneration step, as the purge stream. The heating step may heat theexternal stream to a temperature less than 550° F., less than 500° F.,less than 450° F. or less than 350° F., and may be greater than 50° F.of the gaseous feed stream temperature, greater than 100° F. of thegaseous feed stream temperature or greater than 250° F. of the gaseousfeed stream temperature. For example, the external stream used duringthe purge step may be a temperature in the range between 500° F. andgreater than 50° F. of the gaseous feed stream temperature, in the rangebetween a temperature in the range between 450° F. and the gaseous feedstream temperature; in the range between 450° F. and greater than 100°F. of the gaseous feed stream temperature or 400° F. and greater than200° F. of the gaseous feed stream temperature. The heating of theexternal stream may include passing the stream through a heat exchangeror similar heating unit to increase the temperature of the externalstream. Further, the external stream may be subjected to adepressurization step prior to being passed to the adsorbent bed unitperforming its regeneration step. The depressurization step, which maybe prior to the heating step or following the heating step, may lowerthe pressure of the external stream to a pressure in the range frombetween 0.1 bar absolute (bara) and 100 bara, which is lower than thepressure of the external stream prior to the depressurization step. Thepressure may be lowered by at least 10%, by at least 20% or at least 30%relative to the pressure of the product stream exiting the adsorbentbed. The depressurizing of the external stream may include passing thestream through an expander or flash separation vessel to lower thepressure of the external stream.

As further enhancements, the operating conditions may be adjusted duringthe startup mode to manage the removal of contaminants from theadsorbent bed units. By way of example, the flow rate may be in a rangebetween 25 and 1000 million standard cubic feet per day (MSCFD) duringnormal operation mode, while the flow rate may be in the range between6.25 and 500 MSCFD for startup mode. The flow rate may be increasedduring subsequent purge steps until normal operation mode flow rates arereached. Also, the pressure range of the external stream may be in apressure range between atmospheric pressure and fifty psi aboveatmospheric pressure. In addition, the temperature of the externalstream may be within a temperature range between 20° Celsius (C) aboveatmospheric temperature and 100° Celsius (C) above atmospherictemperature.

In addition, the purge product may be subject to conditioning steps,such as for recovering hydrocarbons from the regeneration step. Forexample, the purge product stream may be cooled or compressed to removecontaminants and may be recycled to be at least a portion of the feedstream or to be at least a portion of the product stream. By way ofexample, a flash separation may be utilized to remove contaminants. Inother configurations, the purge product stream is heated to atemperature 5° F. greater than the dew point of the purge productstream; 10° F. greater than the dew point of the purge product stream;or 20° F. greater than the dew point of the purge product stream. Byheating the purge product stream above the dew point, the heated purgeproduct stream may be used in a subsequent process, such as a gasturbine.

To support the startup mode process, a configuration of the swingadsorption process may include additional bypass conduits and manifoldto pass the external stream or a portion of the external stream toadsorbent bed units during their regeneration step. The configurationmay also include one or more heating units that are upstream of thepurge manifold and configured to heat the external stream prior topassing through the adsorbent bed units and/or that are downstream ofthe purge product manifold and configured to heat the purge productstream. The heating unit may include a heat exchanger, a furnace, or thelike. The configuration may also include one or more depressurizationunits configured to lower the pressure of the external stream. Thedepressurization units may include one or more expanders and/or one ormore separation units. The separation units, which may be a flashseparation vessel, may be configured to separate one or morecontaminants from the external stream. Further, the configuration mayinclude one or more regeneration units that are configured to purify thepurge product stream to remove contaminants from the purge productstream. By way of example, the configuration may include an external gasbypass valve in fluid communication with purge manifold and configuredto provide a flow passage for an external gas stream from an externalgas storage vessel to the purge manifold in a startup mode position andconfigured to block the flow passage of the external gas stream from theexternal gas storage vessel to the purge manifold in a normal operationmode position.

Exemplary embodiments of steps that may be performed in the startup modeprocess are shown in FIG. 4 to FIG. 9. FIG. 4 is an exemplary diagram400 of a startup mode step in accordance with an embodiment of thepresent techniques. In this diagram 400, an adsorbent bed heating stepis shown during the adsorption step of the startup mode cycle. In thisheating step, a feed stream, which may be a wet gas stream or theexternal stream, may be passed via conduit 402 to a heating unit 404.The heating unit 404 may be configured to heat the feed stream to atemperature less than 550° F., less than 500° F., less than 450° F. orless than 350° F., and may be the gaseous feed stream temperature,greater than 50° F. of the gaseous feed stream temperature, greater than100° F. of the gaseous feed stream temperature or greater than 250° F.of the gaseous feed stream temperature. For example, the stream usedduring the purge step may be a temperature in the range between 500° F.and 50° F., in the range between 450° F. and 100° F. or 400° F. and 200°F. (e.g., at a temperature higher than the feed stream temperature).Then, the heated stream may be passed to a depressurization unit 406.The depressurization unit 406 may be configured to lower the pressure ofthe heated stream to a pressure in the range of 0.1 bar absolute (bara)and 100 bara, which is lower than the pressure within the stream priorto the depressurization unit 406 or which may lower the pressure by atleast 10%, by at least 20% or at least 30% relative to the pressure ofthe stream prior to the depressurization unit 406. Then, the resultingstream is passed from the depressurization unit 406 to be flared orrecycled into the process.

FIGS. 5A and 5B are exemplary diagrams 500 and 520 associated withanother startup mode step in accordance with an embodiment of thepresent techniques. In the diagram 500 of FIG. 5A, a blowdown step isshown. In this blowdown step, a blowdown stream, which may be a portionof the gas within the adsorbent bed unit 502, may be passed via conduit504 to a flare (not shown). The blowdown step may be utilized to removea large amount of contaminants, such as water, from the adsorbent bedunit 502.

In FIG. 5B, a diagram 520 of a pressure response 526 is shown along aadsorption axis 522 in moles per kilogram (mol/kg) with respect to apressure axis 522 in bars. In this diagram 520, the response 526 showsequilibrium loading as a function of the partial pressure. As pressurein the adsorbent bed is reduced, the partial pressure lowers resultingin a lower loading on the adsorbent material. This results in desorptionof contaminant from the adsorbent bed which may be conducted away toflare.

FIG. 6 is an exemplary diagram 600 associated with yet another startupmode step in accordance with an embodiment of the present techniques. Inthis diagram 600, an external gas purge step is shown. In this externalgas purge step, an external gaseous stream, which may be a predominatelynitrogen stream, may be passed via conduit 602 to a heating unit 604.The heating unit 604 may be configured to heat the external gas streamto a temperature less than 550° F., less than 500° F., less than 450° F.or less than 350° F., and may be the gaseous feed stream temperature,greater than 50° F. of the gaseous feed stream temperature, greater than100° F. of the gaseous feed stream temperature or greater than 250° F.of the gaseous feed stream temperature. For example, the external streamused during the purge step may be a temperature in the range between500° F. and greater than 50° F. of the gaseous feed stream temperature,in the range between a temperature in the range between 450° F. and thegaseous feed stream temperature, in the range between 450° F. andgreater than 100° F. of the gaseous feed stream temperature or 400° F.and greater than 200° F. of the gaseous feed stream temperature. Then,the heated external gas stream may be passed to the adsorbent bed unit606 as a heated purge stream. The heated purge stream may be passedthrough the adsorbent bed unit 606 to remove one or more contaminantsfrom the adsorbent bed unit 606 and conducted away via conduit 608 as apurge product stream. The purge product stream may be subjected toconditioning and/or flared.

FIG. 7 is an exemplary diagram 700 associated with another startup modestep in accordance with an embodiment of the present techniques. In thisdiagram 700, two adsorbent bed units 702 and 704 are shown performingdifferent steps in the respective startup mode sequence after theproduct stream has reached a level that satisfies the predeterminedthreshold. This step may be performed in one or more cycles followingperformance of the cycles and may be used to startup the downstreamprocesses, such as an NGL system. The first adsorbent bed unit 702 maybe performing an adsorption step, while the second adsorbent bed unit704 may be performing a regeneration step (e.g., a purge step). In theadsorption step, a feed stream may be passed via conduit 706 to firstadsorbent bed unit 702. The feed stream may interact with the adsorbentbed within the first adsorbent bed unit 702 to remove one or morecontaminants from the feed stream and the resulting stream may beconducted away to a downstream process via conduit 710. The externalstream may pass to a heating unit 712 via conduit 714 for theregeneration step for the adsorbent bed unit 704. The heating unit 712may be configured to heat external stream to a temperature, as notedabove. Then, the heated stream may be passed to a depressurization unit716. The depressurization unit 716 may be configured to lower thepressure of the heated stream to a pressure in the range between 0.1 barabsolute (bara) and 100 bara, which is lower than the pressure withinthe stream prior to the depressurization unit 716 or which may lower thepressure by at least 10%, by at least 20% or at least 30% relative tothe pressure of the stream prior to the depressurization unit 716. Then,the resulting stream is passed from the depressurization unit 716 to thesecond adsorbent bed unit 704 as a purge stream during the regenerationstep for the second adsorbent bed unit 704. The purge stream may bepassed through the second adsorbent bed unit 704 to remove one or morecontaminants from the adsorbent bed within the second adsorbent bed unit704 and conducted away via conduit 718 as a purge product stream. Thepurge product stream may be intermingled with a fuel stream, subject toadditional conditioning and/or flared.

FIG. 8 is an exemplary diagram 800 associated with still another startupmode step in accordance with an embodiment of the present techniques. Inthis diagram 800, two adsorbent bed units 702 and 704 are shownperforming different steps in the respective external startup modesequence after the product stream has reached a level that satisfies thepredetermined threshold and after the downstream process is providing apurge stream to the adsorbent bed units 702 and 704. This step may beperformed in one or more cycles following performance of the cycles inFIG. 7, which may include similar reference numbers to FIG. 7, and maybe used to transition to normal operation for the swing adsorptionprocess and/or the downstream processes. In this configuration, the flowrate to the conduit 714 or a valve may be adjusted to decrease theamount of external gas being provided to the heating unit 712 viaconduit 714 and the depressurization unit 716. The adjustment may bebased on the volume of overhead stream being provided from thedownstream process via conduit 802. The adjustment may include using avalve and/or control system in a cascaded configuration, adjusting theflow rate with a valve or blocking flow with one or more valves. Thisprocess may be utilized to transition the swing adsorption process froma RCTSA process to a RCPSA process. Also, this process may be used forthe startup of an NGL process and/or LNG process.

FIG. 9 is an exemplary diagram 900 associated with normal operationmode. In this diagram 900, two adsorbent bed units 902 and 904 are shownperforming different steps in the respective normal operation modesequence after the startup mode is complete. The first adsorbent bedunit 902 may be performing an adsorption step, while the secondadsorbent bed unit 904 may be performing a regeneration step (e.g., apurge step). In the adsorption step, a feed stream may be passed viaconduit 906 to first adsorbent bed unit 902. The feed stream mayinteract with the adsorbent bed within the first adsorbent bed unit 902to remove one or more contaminants from the feed stream and theresulting stream may be conducted away via a conduit 908 to a downstreamprocess. For the regeneration step, the purge stream is passed viaconduit 910 from the downstream process to the second adsorbent bed unit904. The purge stream may be passed through the second adsorbent bedunit 904 to remove one or more contaminants from the adsorbent bedwithin the second adsorbent bed unit 904 and conducted away via conduit912 as a purge product stream. The purge product stream may beintermingled with a fuel stream, provided to a residue gas compressor orother additional conditioning process.

As may be appreciated, the startup mode process may include variouscombination of steps to perform the startup mode process. The startupmodes may use these different step to manage the startup mode sequence.For example, the blowdown step may be performed after the purge step forthe respective adsorbent bed units.

In addition, as another enhancement, the present techniques may includeother enhancements. For example, a heating jacket or blanket may be usedto provide additional heat to the adsorbent bed unit. The additionalheat may be used during startup mode to further provide heat to theadsorbent bed. Specifically, the heating jacket may be disposed adjacentto the adsorbent bed unit and/or manifolds and conduits fluidly coupledto the adsorbent bed unit and configured to heat the adsorbent bed,which may be an electric heating configuration.

In one or more embodiments, the material may include an adsorbentmaterial supported on a non-adsorbent support. The adsorbent materialsmay include alumina, microporous zeolites, carbons, cationic zeolites,high silica zeolites, highly siliceous ordered mesoporous materials, solgel materials, aluminum phosphorous and oxygen (ALPO) materials(microporous and mesoporous materials containing predominantly aluminumphosphorous and oxygen), silicon aluminum phosphorous and oxygen (SAPO)materials (microporous and mesoporous materials containing predominantlysilicon aluminum phosphorous and oxygen), metal organic framework (MOF)materials (microporous and mesoporous materials comprised of a metalorganic framework) and zeolitic imidazolate frameworks (ZIF) materials(microporous and mesoporous materials comprised of zeolitic imidazolateframeworks). Other materials include microporous and mesoporous sorbentsfunctionalized with functional groups. Examples of functional groupsinclude primary, secondary, tertiary amines and other non protogenicbasic groups such as amidines, guanidines and biguanides.

In one or more embodiments, the adsorbent bed unit may be utilized toseparate contaminants from a feed stream during normal operation mode.The method may include passing a gaseous feed stream at a feed pressurethrough an adsorbent bed unit having an adsorbent contactor to separateone or more contaminants from the gaseous feed stream to form a productstream, wherein the adsorbent contactor has a first portion and a secondportion; interrupting the flow of the gaseous feed stream; performing adepressurization step, wherein the depressurization step reduces thepressure within the adsorbent bed unit; performing an optional heatingstep, wherein the heating step increases the temperature of theadsorbent bed unit to form a temperature differential between the feedend of the adsorbent bed and the product end of the adsorbent bed; andperforming a purge step, wherein the purge step reduces the pressurewithin the adsorbent bed unit; performing a re-pressurization step,wherein the re-pressurization step increases the pressure within theadsorbent bed unit; and repeating the steps a) to e) for at least oneadditional cycle.

Further, in one or more embodiments, the adsorbent bed unit may includean adsorbent bed that can be used for the separation of a target gasform a gaseous mixture. The adsorbent is usually comprised of anadsorbent material supported on a non-adsorbent support, or contactor.Such contactors contain substantially parallel flow channels wherein 20volume percent, preferably 15 volume percent or less of the open porevolume of the contactor, excluding the flow channels, is in poresgreater than about 20 angstroms. A flow channel is taken to be thatportion of the contactor in which gas flows, if a steady state pressuredifference is applied between the point or place at which a feed streamenters the contactor and the point or place at which a product streamleaves the contactor. In the contactor, the adsorbent is incorporatedinto the wall of the flow channel.

In one or more embodiments, when using RCTSA or an integrated RCPSA andRCTSA process, the total cycle times are typically less than 600seconds, preferably less than 400 seconds, preferably less than 300seconds, preferably less than 250 seconds, preferably less than 180seconds, more preferably less than 90 seconds, and even more preferablyless than 60 seconds. In other embodiment, the rapid cycle configurationmay be operated at lower flow rates during startup mode as compared tonormal operation mode, which may result in the cycle durations beinglonger than the cycle durations during normal operation mode. Forexample, the startup mode cycle duration may be for a period greaterthan 1 second and less than 2400 seconds, for a period greater than 1second and less than 1500 seconds, for a period greater than 1 secondand less than 1000 seconds, for a period greater than 1 second and lessthan 600 seconds, for a period greater than 2 second and less than 800seconds, for a period greater than 2 second and less than 400 seconds,for a period greater than 5 second and less than 150 seconds or for aperiod greater than 5 second and less than 90 seconds.

In view of the many possible embodiments to which the principles of thedisclosed invention may be applied, it should be recognized that theillustrative embodiments are only preferred examples of the inventionand should not be taken as limiting the scope of the invention.

What is claimed is:
 1. A process for removing contaminants from agaseous feed stream with a swing adsorption process, the processcomprising: a) performing a purge step, wherein the purge step comprisespassing an external gas stream through an adsorbent bed unit to removeone or more contaminants from an adsorbent bed within a housing of theadsorbent bed unit to form a purge product stream; b) performing one ormore adsorption steps, wherein each of the one or more adsorption stepscomprise passing a gaseous feed stream through an adsorbent bed unithaving an adsorbent bed to separate one or more contaminants from thegaseous feed stream to form a product stream; c) determining whether theproduct stream is within a specification for a contaminant; d) if theproduct stream is within the specification, passing the product streamto a downstream process; e) if the product stream is not within thespecification, repeating the steps a) to d) for at least one additionalcycle; wherein the process further comprises mixing a slip stream fromthe downstream process with the external gas stream prior to performingthe purge step.
 2. The process of claim 1, further comprising adjustingthe amount of external gas stream utilized in the performing a purgestep based on the amount of the slip stream from the downstream process.3. The process of claim 1, further comprising heating the external gasstream prior to passing the external gas stream through an adsorbent bedunit.
 4. The process of claim 3, wherein the external gas stream isheated to a temperature in the range between 500° F. and greater than50° F. of the gaseous feed stream temperature.
 5. The process of claim3, wherein the external gas stream is heated to a temperature in therange between 450° F. and the gaseous feed stream temperature.
 6. Theprocess of claim 1, further comprising heating the purge product stream,wherein the purge product stream is heated to a temperature 10° F.greater than the dew point of the purge product stream.
 7. The processof claim 5, further comprising: separating one or more contaminants fromthe purge product stream to form conditioned purge product stream; andmixing the conditioned purge product stream with external gas sourcestream to form the external gas stream.
 8. The process of claim 1,wherein the purge stream is passed in a countercurrent directionrelative to the direction of the feed stream and wherein a temperaturedifferential exists at the end of the purge step in a range between 100°F. and 400° F., wherein the temperature differential is the differencein temperatures between a feed end of the adsorbent bed and a productend of the adsorbent bed.
 9. The process of claim 1, wherein the cycleduration is for a period greater than 1 second and less than 2400seconds.
 10. The process of claim 1, wherein the gaseous feed stream isa hydrocarbon containing stream having greater than one volume percenthydrocarbons based on the total volume of the feed stream.
 11. Theprocess of claim 1, wherein the gaseous feed stream compriseshydrocarbons and CO₂, wherein the CO₂ content is in the range of twohundred parts per million volume to less than or equal to about 2%volume of the gaseous feed stream.
 12. The process of claim 1, whereinthe adsorbent bed unit is configured to lower the carbon dioxide (CO₂)level to less than 50 parts per million.
 13. The process of claim 1,wherein the gaseous feed stream comprises hydrocarbons and H₂O, whereinthe H₂O is in the range of 0.2 parts per million volume to saturationlevels in the gaseous feed stream.
 14. The process of claim 1, whereinthe gaseous feed stream comprises hydrocarbons and H₂O, wherein the H₂Ois in the range of 100 parts per million volume to 1500 parts permillion volume.
 15. The process of claim 1, further comprising: passingthe product stream from the adsorbent bed unit to a liquefied naturalgas (LNG) process unit; and separating a flash fuel stream from the LNGprocess unit and utilizing the flash fuel stream from the LNG processunit as at least a portion of the slip stream.
 16. The process of claim1, further comprising: passing the product stream from the adsorbent bedunit to a cryogenic natural gas liquid recovery (NGL) process unit; andseparating an overhead stream from the NGL process unit and utilizingthe overhead stream from the NGL process unit as at least a portion ofthe slip stream.
 17. The process of claim 1, wherein the cycle durationis greater than 2 seconds and less than 800 seconds.
 18. The process ofclaim 1, wherein the external gas stream is a nitrogen containing streamhaving greater than one volume percent nitrogen based on the totalvolume of the feed stream.
 19. The process of claim 1, wherein theexternal gas stream comprises a predominately nitrogen stream comprisingless than 0.1 ppm of water.
 20. The process of claim 1, wherein theexternal gas stream comprises a predominately nitrogen stream comprisingless than 10 ppm of water.
 21. The process of claim 1, wherein theexternal gas stream comprises at least one of nitrogen, methane, helium,hydrogen or any combination thereof.